v0.3.0

This release updates Buildroot to 2020.02 and upgrades gcc from 8.3 to 9.2.
While this is a minor version bump due to the Buildroot release update, barring
advanced usage of Nerves, this is a straightforward update from v0.2.1.

• Updated dependencies
  • nerves_system_br v1.11.0
  • linux 5.4.26
  • Erlang 22.2.8
• Enhancements
  • Enable linux kernel module for CMOS RTC. This update will continue to work
    in conjunction with nerves_time for clock sync.